Adjustable dumbbell



FIG. 1 is a perspective view of an adjustable dumbbell showing our new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a bottom plan view thereof;

FIG. 4 is a side elevation view thereof, the other side being identical thereto; and,

FIG. 5 is an end elevation view thereof, the other end being identical thereto.

The broken line portions of the disclosure are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for an adjustable dumbbell, as shown. 